GB891246A - Magnetic pressure indicator - Google Patents

Abstract

891,246. Filters; thermostatic clogging indicators. PALL CORPORATION. March 30, 1960, No. 11240/60. Class 46. The upper end of a cylindrical bore 15, Fig. 3, is in communication via ducts 20a, 20 with the inlet conduit to a filter (not shown), whilst its lower end is in communication with the outlet conduit (or atmosphere or a vacuum). A tubular piston 14 containing a magnet 10 is urged downwards in the bore by the pressure differential and upwards by a spring 16. Upon increase of the pressure differential beyond a predetermined maximum the piston is forced downwards, magnetic attraction of an upper magnet 11 slidable in a bore 27 above a partition 12 is thereby diminished, and the upper magnet with a cap 28 secured thereto is moved upwards by a spring 31 to protrude through an opening 34 in a drum 33. (When a sleeve 40 with its contents is omitted such protrusion serves as an indication of clogging). As shown, the cap 28 operates the switch arm 43 of an alarm-device switch 39 through a two-armed lever 42, 45, pivoted at 42a. If movement of the lever (and thereby of cap 28) is suitably limited by a setscrew 44 the upper magnet may be automatically re-attracted when the lower magnet returns to its upper position. Cap 28 has an outer skirt 29 with flange 32, the flange being engaged by a bimetallic element 37, 38, Figs. 2 and 3, to prevent rising of the magnet 11 when the temperature is abnormally low and the excess pressure is consequently due only to high viscosity of the liquid (e.g. oil) being filtered. An annular filter element 21 is interposed between duct 20 and the lower piston assembly. In Fig. 4 (not shown), the filter element 21 is dispensed with : instead, a collapsible bellows is mounted between the top of the piston 14 and bore 15, 10 or 11 need not be a magnet, but only of ,magnetic material.